High-efficiency video coding (HEVC) is the latest video coding standard developed by the Joint Collaborative Team on Video Coding (JCT-VC) that combines expertise of both the International Telecommunication Union (ITU) and the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC). Like its predecessor, advanced video coding (AVC), HEVC uses high-level syntax (HLS) elements to define the structure of the output bitstream and to provide information that applies to multiple pictures or to multiple coded block regions within a picture. HLS elements may be carried in parameter sets that contain control information in accordance with which video data are encoded and subsequently decoded.
Among other things, parameter sets include information that compels various encode/decode operations to be overridden or bypassed. For example, in conventional coding operations, a transform is performed on a block of data to convert the sample data contained in the block into its frequency representation. While this may improve coding efficiency on blocks having certain characteristics, e.g., highly variable graphic content, higher coding efficiency of some blocks is achieved if the transform operation is omitted. Accordingly, in HEVC, a block of video data can be coded without a transform operation, referred to as transform skipping, which is indicated by an HLS element transform_skip_flag. When transform_skip_flag is equal to one (1), the associated data block is coded in the transform skip mode. Otherwise, a transform is applied to the associated block.